Building decontamination with vaporous hydrogen peroxide

ABSTRACT

When microbial contamination is introduced into a room ( 20 *) of an enclosure, such as a building, an HVAC system including supply ductwork ( 16 ) and a return ductwork ( 34 ) is decontaminated with hydrogen peroxide vapor. A decontamination controller ( 46 ) operates controllable baffles ( 22 ) at outlet registers ( 20 ), temporary controllable baffles ( 44 ) at inlet registers ( 30 ), and a blower system ( 10 ) to circulate hydrogen peroxide vapor from hydrogen peroxide vapor generators ( 42 ) through the ductwork in both forward and reverse directions. Further, at least portions of the baffles are closed to create dwell times in which the hydrogen peroxide vapor resides in the ductwork with minimal or turbulent flow.

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial No. 60/444,073, filed on Jan. 31, 2003, which isincorporated herein in its entirety, by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to the microbial decontaminationarts. It finds particular application in conjunction with sporicidaldecontamination of heating, ventilation, and cooling (HVAC) systems andwill be described with particular reference thereto. However, it is tobe appreciated that the present invention is also applicable to othertypes of microorganisms and to other decontamination applications.

[0003] HVAC systems typically include a series of delivery ducts, whichdeliver heated or cooled air from one or more heat exchangers toindividual rooms or offices. The duct is typically largest in crosssection adjacent the heat exchanger and diminishes in cross section asit branches to supply treated air to the individual rooms and offices.Typically, baffles at the register outlets and, in some systems, atvarious points along the ductwork system, control the relative amountsof air delivered to each room or register outlet. In modernconstruction, the baffles are sometimes motorized in order to provideindividual room temperature control. The automated baffles are also usedfor safety, such as to shut down the supply of air if a fire isdetected.

[0004] HVAC systems typically include a return system for returning airfrom the rooms to the heat exchanger. Some systems use a central return,which delivers return air from a central location to the heat exchangerto be retreated and recirculated. Other systems include a plenum, oftendefined by the open space above acoustic ceiling tiles, through whichair is drawn back to the heat exchanger. Often, the plenums interconnectwith ductwork, which conveys the return air back to the heat exchanger.Other systems include ductwork extending from a return register in eachroom. These individual ducts merge into progressively larger ducts asthey approach the heat exchanger.

[0005] Blower motors and filters located adjacent the heat exchangerpropel the treated air through the delivery duct system to theindividual rooms and draw return air back to and through the heatexchanger. The ducts themselves are typically galvanized steel oraluminum. Portions of the ductwork or plenum may include acousticmaterial. In older buildings, the ductwork may have an accumulated layerof dust, dirt, and grease.

[0006] Large enclosures, such as rooms and buildings tend to becomecontaminated with a wide variety of microbial contaminants, includingbacteria, molds, fungi, yeasts, and the like. These microorganismsthrive in damp spaces, such as behind walls, in plaster, under countersin bathroooms, and in ductwork and tend to be very difficult toeradicate. Some contaminants are brought into the room in the air, boththrough doorways, windows and the like as well as through ventilationsystems. Contaminants are also carried into the room on the clothing orperson by people using the room and from breathing. Some microbes causea musty smell. Others can infect later users of the room. Additionally,there is a possibility that a room may be intentionally contaminatedwith pathogenic microorganisms, such as anthrax spores, smallpox virus,or the like. Some contaminants, such as tobacco smoke, body perfume, andmedicinal odors are non-microbial.

[0007] When microbial contamination is introduced into a building, suchas an Anthrax spore laced letter, the microbes tend to become airborneand are drawn into and pumped through the HVAC system. Killing sporesand other microbes in the relatively inaccessible ductwork of the HVACsystem has proven difficult.

[0008] The present invention provides a new and improved decontaminationsystem and method which overcome the above-referenced problems, andothers.

SUMMARY OF THE INVENTION

[0009] In accordance with one aspect of the present invention, abuilding decontamination system is provided. The system includes a meansfor circulating air through a ductwork system and a means for supplyinga decontamination vapor to the ductwork system to be circulated throughit.

[0010] In accordance with another aspect of the present invention, amethod of decontaminating buildings is provided. A vapor decontaminantis circulated through an HVAC ductwork system and associated rooms ofthe building.

[0011] One advantage of the present invention resides in its efficacy inmicrobially decontaminating ductwork.

[0012] Another advantage of the present invention resides in itsefficacy of decontaminating buildings.

[0013] Still further advantages of the present invention will becomeapparent to those of ordinary skill in the art upon reading andunderstanding the following detailed description of the preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention may take form in various parts and arrangements ofparts. The drawings are only for purposes of illustrating a preferredembodiment and are not to be construed as limiting the invention.

[0015]FIG. 1 is a diagrammatic illustration of an HVAC system incombination with a vapor hydrogen peroxide decontamination system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Commercial buildings and other large enclosures typically includeseveral heat exchanger and delivery and return ductwork subsystems orzones, each heating or cooling a distinct area of the building. In eachof a plurality of heating and cooling zones of a large building, a fanor blower 10 draws air through a heat exchanger 12 and a filter 14. Thefan propels heated air (in the winter) or cooled air (in the summer)through a delivery duct system 16. The delivery duct system includesbranches, turns, and various angles. Adjustable baffles 18 are locatedat various points within the delivery duct system to control therelative airflow to the various branches.

[0017] The delivery duct system delivers heated or cooled air to each ofa plurality of regions, such as offices or other rooms 20. At each roomor office, a heat delivery register 21 with a control valve or baffle 22is connected with the delivery duct system. Preferably, each room oroffice further includes a thermostat 24. In a preferred modern officeenvironment, the thermostats 24 are connected with a central electroniccontrol 26, which controls the corresponding register valve or baffle 22to regulate temperature within each room or office. The controllerfurther controls a source 28 of heated or cooled liquid to the heatexchanger, such as cooling tower, to be sure that an adequate supply ofheating or cooling is delivered to maintain all of the rooms or officesat the selected temperatures. In older buildings, the baffle 22 at theregisters 21 is manually adjustable.

[0018] On a return side, each room or office includes a return register30 that interconnects with one or more common plenums 32, such as an airspace above the acoustic ceiling of several offices. The plenum isconnected with a return duct system 34 through which air is drawn fromthe plenum back to the filter 14 and heat exchanger 12. Alternately, thereturn registers can be connected directly to the return ducts.

[0019] When contamination is introduced into the building, it may bedone by opening a letter or package in one of the offices 20*. If doorsto the office are open, some of the airborne spores will be carried intoan adjacent hallway and other offices. Many of the spores will be drawnthrough the return register 30* into the plenum 32 where some of thespores or other microbes will be deposited on plenum surfaces. Most ofthe spores will be drawn into the return duct 34 where many will againbe deposited on return duct surfaces. Because the filter 14 is typicallya dust filter and not a HEPA filter, the filter typically traps some ofthe spores, but permits many others to pass into the heat exchanger 12and into the delivery duct system 16. Moreover, some of the spores willpass down the hallway into adjoining HVAC subsystems and be pulled intoother return and delivery duct systems.

[0020] First, to minimize the spread of the microbial decontamination,those offices or rooms in which mail will be opened are equipped with apanic switch 40 that is interconnected with the controller 26 forimmediately stopping the circulation of air through the HVAC system.Where the baffles 22 are controllable, the HVAC system also immediatelycloses all baffles.

[0021] Alternatively or additionally, one or more automated detectors 41for one or more hazardous airborne materials are located in the mailhandling room. The detector(s) are interconnected with the controllerfor immediately stopping the circulation of air through the HVAC system.An associated alarm system is activated by the controller in the eventthat hazardous material is detected.

[0022] Once all personnel have been evacuated and decontaminated asnecessary, the source of the microbial contamination is removed ordestroyed.

[0023] Next, the office or offices that were directly contacted by thesource of contamination are decontaminated with a gaseous decontaminant,preferably hydrogen peroxide vapor. More specifically to the firstembodiment, a hydrogen peroxide vapor generator 42 is wheeled into orconnected with the contaminated room or office 20*. The inlet register21* is sealed and the return register 30* is sealed. When automatedbaffles are available, the automated baffles can be used to seal theregisters. Alternately, the registers are covered, such as with plasticor metal foil. The covering can be held in place with tape, magnets, orthe like. The vapor hydrogen peroxide generator 42 fills the room oroffice 20* with hydrogen peroxide vapor which is held in the room withan appropriate concentration and for an appropriate time to kill themicrobial contamination at issue. A decontamination control system 46controls the supply of vapor to the room 20*.

[0024] Next, or before decontaminating the most contaminated room, thebuilding is cordoned off or partitioned in accordance with HVACsubsystems or zones. In general, any of the HVAC subsystems might becontaminated with the microbes. The microbes may have been circulatedthrough the air, particularly if the HVAC systems were not shut offpromptly. Further, microbes may have been carried from zone to zone bypersonnel evacuating the facility. The HVAC subsystems can bedecontaminated one by one, or concurrently by a plurality ofdecontamination teams. Preferably, the decontamination process isstarted at the HVAC subsystems that are most remote from thecontamination site 20*.

[0025] To decontaminate each HVAC subsystem, vapor hydrogen peroxide iscirculated through each HVAC subsystem. It will be noted that with asteady-state flow, certain areas of the ductwork will be shielded fromflowing hydrogen peroxide vapor. For example, turbulent flow at squarecorners will tend to leave an untreated or cold spot just past thecorner. Similarly, ridges in the ductwork, baffles, and the like willhave untreated or cold spots on their downstream or leeward sides. To besure that all of these areas are treated, once the ductwork is filledwith vapor hydrogen peroxide and plain air is flushed out, the airflowis stopped and permitted to dwell in the ductwork system for apreselected duration. Then, circulation is recommenced. Preferably, eachtime circulation is recommenced, the flow direction through the ductworkis reversed. The reversed flow preferably continues until the partiallyspent vapor hydrogen peroxide that had dwelled in the ductwork system isflushed out and replaced by new vapor hydrogen peroxide. Circulation isagain stopped for another dwell period. The number of times that thisfill, dwell, and flush cycle is repeated will vary with the type ofdecontamination and the ductwork system. For example, ductwork with anaccumulation of dust and dirt may be more difficult to decontaminatethan a ductwork system that has a clean, smooth metallic surface.

[0026] The entire HVAC subsystem need not be subject to the fill, dwell,and flush stages concurrently. Rather, in another embodiment, once theductwork is filled, a first fraction of the inlet and outlet registersis closed to create a dwell phase while the vapor hydrogen peroxidecontinues to circulate through other parts of the same HVAC subsystem.After the first portion of the HVAC system has undergone the dwellphase, those registers can be opened for a flush a refill phase whileanother group of registers are closed to bring that section of theductwork into the dwell phase. In this manner, the open and closedregisters are cycled such that all duct areas receive a combination offlowing and static vapor.

[0027] One or more of temperature, vapor concentration, and flow ratemonitors 48 in the incoming and/or return ductwork or room optionallymeasure properties of the vapor, allowing the decontamination controlsystem 46 to adjust decontamination parameters such as vaporconcentration, flow rates, room temperatures, decontamination time, andthe like to ensure decontamination.

[0028] Preferably, the anti-microbial vapor is introduced in the roomsor offices for circulation. This can be achieved by placing a vaporhydrogen peroxide generator in each room or by connecting a largergenerator to a plurality of rooms with temporary, portable ducts. In analternate embodiment, the hydrogen peroxide generator is tapped into theheat exchanger. This can be done by cutting through the side wall of theheat exchanger or associated ductwork, by interconnecting through theopenings for changing filters, through access panels, or the like. Whenthe vapor is introduced at a central location, like the heat exchanger,a supplemental blower associated with the generator can blow the vaporinto both the feed and return ducts, concurrently.

[0029] In another embodiment, the airflow through the ductwork ispulsed. That is, ductwork is designed for smooth, laminar flow. Thecirculation of the air is pulsed into high and low or no velocityperiods to create turbulence to bring the vapor into contact with allsurface portions.

[0030] To facilitate remote, automated control, a temporary baffle is inthe form of a balloon is inserted in the input registers without remotecontrolled baffles and into return registers. The balloon is inflated toblock or substantially block the outlet during the pause portions and isdeflated to permit fluid flow during the forward and reverse flowportions of the cycle. The balloons can be controlled pneumatically oran associated electric pump can be controlled electrically.

[0031] In another embodiment, electrically operated baffles 44 areinstalled temporarily over registers 21 and/or registers 30 that do nothave controllable baffles. The electrically operated baffles are pluggedinto a convenient electrical outlet in the room to provide a source ofelectricity. Each baffle preferably includes a radio receiver forreceiving open and close commands. Baffles that leak slightly areadvantageous for preventing dead legs in the ductwork which aredifficult to fill with the vapor. More preferably, each of the remotelyoperable baffles is operable by the decontamination control system 46.The decontamination control system 46 is also connected with themonitors and the blower for circulating air through the ductwork forautomatically controlling a decontamination cycle.

[0032] Further, concentration monitors 48 are preferably incorporated ateach temporary baffle to provide the decontamination control system 46with immediate feedback of vapor concentrations at the variousregisters. Additional concentration sensors 48 are preferably mounted inthe individual offices, at the heat exchanger, and at other accessiblelocations in the ductwork. The sensors detect the concentration ofhydrogen peroxide and/or water vapor in the room and ductwork. Thesensors are connected with the decontamination control system 46. Thecontrol system responds to the detected concentrations of water vaporand/or hydrogen peroxide by adjusting one or more of hydrogen peroxideconcentration in the vapor, flow rates, exposure times, and the like tomaintain suitable conditions for decontamination. For example, thedecontamination control system 46 dynamically adjusts thedecontamination cycles to maintain preselected minimum hydrogen peroxideconcentrations at all locations. The decontamination control system 46further controls the vapor hydrogen peroxide generator(s) 42 to increaseor decrease vapor production rates, as may be necessary, to maintain thepreselected concentrations. The decontamination control system 46optionally models the duct system in order to determine optimal supplyand flow rates, cycle timing, and the like. In this manner, thedecontamination controller 46 takes into account long runs, unbalancedbranching of the supply and return ducts, potential cold spots in theductwork, and other problematic locations. The control system mayinclude a processor which is preprogrammed to optimize and implement adecontamination cycle which includes flowing vapor through the ductsystem in one direction, allowing the vapor to stagnate in the system,and flowing the vapor in an opposite direction.

[0033] When the ductwork is configured such that additional hydrogenperoxide needs to be added at various locations around the ductwork,flexible hoses are connected with the vapor hydrogen peroxide generatorand threaded through the ducts to such locations. Preferably, theabove-described vapor cycles are performed first. If there is any dirt,dust, or loose materials in the ductwork, threading hoses through theduct system could dislodge them, allowing them to fall, cover, andshield spores or other microbes. The hose, particularly a porous hose,delivers high concentrations of the vapor directly to problem areas ofthe duct. In one embodiment, the hose has high velocity nozzles suchthat the vapor is ejected at high velocities deliberately disturbing andsuspending dirt and dust that may be lining the walls of the ductwork.The blower circulates the disturbed and suspended dust and dirtparticles to HEPA filters located at the heat exchanger and at eachregister. The individual HEPA are removed and subject to a heavy-dutydecontamination process, such as immersion in a liquid decontaminant,incineration, or the like. The flexible hose or other flexible devicemay also be used to carry baffles into the ductwork to redirect vapor toportions of the ductwork with low flow rates and low vaporconcentrations. The flexible hose can also carry flow monitors tovarious points in the ductwork. Flow velocity, temperature, and othermonitors, computer modeling, and the like are all used to optimize thedecontamination process. The flexible elements can also carrycontamination detectors, biological sampling devices, and the like.

[0034] Further, spore strips 60 can be positioned at the registers inthe heat exchanger, or at various locations in the ductwork prior totreatment. After the treatment has been completed, the spore strips areincubated to assure successful decontamination.

[0035] The system is suited to decontamination of a wide variety ofbuildings, including offices, research facilities, factories, schools,hospitals, and hotels. Portions of buildings having individual ductworksystems can also be treated, such as hotel suites having a bathroom inaddition to one or more bedroom areas. Passenger vehicles havingductwork, such as ships, airplanes, and the like may also bedecontaminated.

[0036] Different levels of decontamination are contemplated. As usedherein, the term “decontamination,” and its equivalents, is intended toencompass both microbial decontamination as well as chemicaldecontamination—the destruction of chemical agents, or their conversionto harmless or odorless compounds. Decontamination also encompasses theneutralizing of unpleasant odors, such as tobacco smoke, perfume, orbody odor residues, and odors and dampness due to molds. “Microbialdecontamination” is used herein to encompass the destruction ofbiological contaminants, specifically, living microorganisms, and alsothe destruction or inactivation of pathogenic forms ofproteinaceous-infectious agents (prions). The term microbialdecontamination encompasses sterilization, the highest level ofbiological contamination control, which connotes the destruction of allliving microorganisms. The term also includes disinfection, thedestruction of harmful microorganisms, and sanitizing, which connotesbeing free from germs. “Chemical decontamination” is intended toencompass the destruction of pathogenic chemical agents or theirconversion to less harmful or odiferous species.

[0037] Exemplary biological contaminants which are destroyed in thedecontamination process include bacterial spores, vegetative bacteria,viruses, molds, and fungi. Some of these are capable of killing orcausing severe injury to mammals, particularly humans. Included amongthese are viruses, such as equine encephalomyelitis and smallpox, thecoronavirus responsible for Severe Acute Respiratory Syndrome (SARS);bacteria, such as those which cause plague (Yersina pestis), anthrax(Bacillus anthracis), and tularemia (Francisella tularensis); and fungi,such as coccidioidomycosis; as well as toxic products expressed by suchmicroorganisms; for example, the botulism toxin expressed by the commonClostridium botulinium bacterium.

[0038] Also included are the less harmful microorganisms, such as thoseresponsible for the common cold (rhinoviruses), influenza(orthomyxoviruses), skin abscesses, toxic shock syndrome (Staphylococcusaureus), bacterial pneumonia (Streptococcus pneumoniae), stomach upsets(Escherichia coli, Salmonella), and the like.

[0039] Exemplary pathogenic chemical agents include substances which areoften referred to as chemical warfare agents, such as poison gases andliquids, particularly those which are volatile, such as nerve gases,blistering agents (also known as vesicants), and other extremely harmfulor toxic chemicals. As used herein, the term “chemical pathogenic agent”is intended to include only those agents which are effective inrelatively small dosages to substantially disable or kill mammals andwhich can be degraded or otherwise rendered harmless by a process whichincludes oxidation.

[0040] Exemplary chemical pathogenic agents include choking agents, suchas phosgene; blood agents, which act on the enzyme cytochrome oxidase,such as cyanogen chloride and hydrogen cyanide; incapacitating agents,such as 3-quinuclidinyl benzilate (“BZ”), which blocks the action ofacetylcholine; vesicants, such as di(2-chloroethyl) sulfide (mustard gasor “HD”) and dichloro(2-chlorovinyl)arsine (Lewisite); nerve agents,such as ethyl-N, N dimethyl phosphoramino cyanidate (Tabun or agent GA),o-ethyl-S-(2-diisopropyl aminoethyl) methyl phosphono-thiolate (agentVX), isopropyl methyl phosphonofluoridate (Sarin or Agent GB),methylphosphonofluoridic acid 1,2,2-trimethylpropyl ester (Soman orAgent GD).

[0041] Hydrogen peroxide vapor is a particularly effective microbial andchemical decontaminant because it has broad spectrum activity against awide variety of pathogenic microorganisms and chemical pathogenicagents, such as hard to destroy spores of Bacillus stearothermophilus,Bacillus anthracis, smallpox virus, and the like. It is also effectiveat or close to room temperature (e.g., 15-30° C.), making it suitablefor decontamination of enclosures with little or no heating. Hydrogenperoxide vapor has a good material compatibility, rendering it safe foruse with a variety of equipment and materials, including electronicequipment, soft furnishings, brass and chrome fixtures, and the like. Italso degrades to water and oxygen over time, which are not harmful topeople subsequently entering the treated space. Where low levels ofhydrogen peroxide (about 1 ppm, or less) remain in the room afterdecontamination, this is not considered to pose a risk to the occupants.

[0042] The invention has been described with reference to the preferredembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

Having thus described the preferred embodiments, the invention is nowclaimed to be:
 1. A decontamination system for an enclosure comprisingductwork for transporting air to a plurality of regions of theenclosure, the system comprising: a means for circulating air through aductwork system; a means for supplying decontamination vapor to theductwork system to be circulated therethrough.
 2. The system as setforth in claim 1 further including controllable baffles disposedadjacent registers between the ductwork and rooms.
 3. The system as setforth in claim 2 further including at least one of temperature, vaporconcentration, and flow rate monitors disposed in conjunction with thecontrollable baffles.
 4. The system as set forth in claim 3 furtherincluding: a decontamination controller connected with the controllablebaffles, the monitors, and the means for circulating air through theductwork for automatically controlling a decontamination cycle.
 5. Thesystem as set forth in claim 4 wherein the decontamination controllerincludes: a processor which is preprogrammed to optimize and implement adecontamination cycle which includes flowing vapor through the system inone direction, allowing the vapor to stagnate in the system, and flowthe vapor in an opposite direction.
 6. The system as set forth in claim4 wherein the decontamination controller controls at least the bafflesand the means for circulating air through the ductwork to createturbulent flow.
 7. The system as set forth in claim 1 wherein the meansfor supplying decontamination vapor includes: a hydrogen peroxide vaporgenerator.
 8. The system of claim 1, wherein the enclosure comprises abuilding or portion thereof and the regions comprise rooms.
 9. Thesystem as set forth in claim 2, further including: at least one of thecontrollable baffles including a temporary baffle which is selectivelyinserted into a portion of the ductwork system.
 10. A method ofdecontaminating buildings comprising: circulating a vapor decontaminantthrough HVAC ductwork and associated rooms.
 11. The method as set forthin claim 10 wherein the vapor decontaminant includes hydrogen peroxidevapor.
 12. The method as set forth in claim 11 further including:circulating the hydrogen peroxide vapor through the ductwork in onedirection, circulating the hydrogen peroxide vapor through the ductworkin an opposite direction, and allowing the hydrogen peroxide vapor todwell in the ductwork.
 13. The method as set forth in claim 12 furtherincluding: automatically opening and closing baffles at registersbetween the HVAC ductwork and individual rooms.
 14. The method as setforth in claim 13 further including: monitoring at least one oftemperature, flow velocity, and vapor concentration; and controlling theopening and closing of the baffles in accordance with the monitoring.15. The method as set forth in claim 10 further including: creatingturbulent flow in the ductwork.
 16. The method as set forth in claim 10wherein the HVAC ductwork includes a plurality of independent HVACductwork subsystems, the method further including: decontaminating HVACsubsystems more remote from a contamination site within the building andprogressively decontaminating HVAC subsystems closer to thecontamination site.
 17. The method as set forth in claim 10, furtherincluding: connecting a temporary baffle with the ductwork; andcontrolling the temporary baffle to control the flow of vapordecontaminant from the ductwork to at least one of the regions.